Safety Precautions — Aircraft & Workshop
Safe working with electricity, gases, oils and chemicals; classes of fire and the correct extinguishing agent for each; action on discovering a fire.
Safety precautions — summary notes
Free- Safe working covers electricity, gases, oils and chemicals, and the correct response to fire. The aircraft must be made safe before work starts: electrical power isolated, systems depressurised, warning notices and ground locks fitted, and the area cordoned where needed.
- Fires are classified by the material burning. Class A solids take water or foam; Class B flammable liquids take foam, CO₂ or dry powder; Class C gases require the supply to be isolated first; Class D metals need a special dry powder; Class F cooking oils need wet chemical.
- Fires in live electrical equipment are NOT a separate class — electricity is an ignition source, not a fuel. Use CO₂ or dry powder, isolate the power, and never water or foam, which conduct.
- Wheel and brake fires take dry powder, never water — water on an overheated assembly can flash to steam and burst it. Approach fore and aft, never in line with the axle, because a fusible plug or wheel can fail explosively.
- Oxygen supports combustion and reacts violently with oil and grease, so oxygen equipment must be scrupulously clean and only approved lubricants used. Nitrogen is inert but asphyxiates by displacing air in confined spaces.
- Electrical safety: isolate and prove dead, treat capacitors and CRTs as charged after shutdown, and never work alone on high-energy systems.
- ⚠ Exam trap: water on an electrical or brake fire is the classic wrong answer, and CO₂ in a confined space is itself an asphyxiation hazard.
- Fire classes
- A solids · B liquids · C gases · D metals · F cooking oils
- Agent rule
- electrical → CO₂ / dry powder · wheels & brakes → dry powder · never water on either
A fire starts in an energised avionics rack. State the agent and the first action.
Isolate the electrical power, then use CO₂ or dry powder. Water and foam conduct and would endanger the operator; removing the ignition source is as important as applying the agent.
Why must a technician approach a suspected overheated brake unit from fore and aft rather than from the side?
An overheated wheel can fail explosively, and the debris is thrown outward along the axle line. Approaching fore and aft keeps the technician out of that path; the fusible plugs are designed to deflate the tyre before it bursts, but the approach discipline still applies.
Safety precautions concept map
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